Accession Number:

ADA179214

Title:

Thermal Shock Resistance of Mullite-Based SiC-Whisker Composites.

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s):

Report Date:

1986-12-01

Pagination or Media Count:

114.0

Abstract:

The influence of the addition of silicon carbide SiC whiskers and zirconia on the material properties and constants of pure mullite was examined. SiC whisker weight percentages of 0, 10, 20, and 30 were examined, and a zirconia content of 36.1 wt. was studied. A theoretical approach similar to Hasselmans high-E, low-E theory was used to determine the theoretical values of the material properties which were then compared to experimental results. Using experimental and theoretical values for Youngs modulus of elasticity, bend strength, mean coefficient of thermal expansion, thermal diffusivity, and Poissons ratio, the thermal stress resistance parameters were calculated, and compared to experimental results for critical quench temperatures. Microstructures were characterized by x-ray diffraction XRD analysis, chemical analysis, density determinations, light microscopy LM, and scanning electron microscopy SEM. The mullite was alumina-rich with particles of silica present. Whisker composites contained 2H, 4H, and 15R polytypes of SiC and impurities from the whisker. Mullite-zirconia microstructures contained partially-stabilized zirconia with monoclinictetragonal ratios of 90. Increasing SiC whisker content decreased the Poissons ratio and mean coefficient of thermal expansion of the specimen and increased the elastic modulus, bend strength, and thermal diffusivity of the composites.

Subject Categories:

  • Laminates and Composite Materials
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE